Conversion of hydrocarbons



Patented Feb. 17, 1948 CONVERSION OF HYDBOCARBONS Rowland 0. Hansfordand Alexander N. Sachanen, Woodbury,-N. J., assignors to Socony- VacuumOil Company, Incorporated, a corporation of New York No Drawing.Application August 9, 1944, Serial No. 548,786

This invention relates generally to cracking of petroleum stocks, and ismore particularly concerned with a method of catalytic cracking ofpetroleum stocks, whereby the yields of hydrocarbons boiling within thegasoline boiling range, are substantially increased.

Cracking is a well known chemical process and generally connotesoperations for converting heavy hydrocarbon molecules into lighthydrocarbon molecules. The decomposition or the breakdown of the heavyhydrocarbon molecules into lighter ones, is accompanied by theconcurrent formation of even heavier hydrocarbon molecules and by theproduction of solid material referred to as coke. Cracking wasoriginally carried out non-catalytically, at temperatures of the orderof 7501l00 F. with the charge stocks mostly in the liquid phase.However, due to the demand for anti-knock gasoline, and since the motorfuels produced by catalytic cracking operations, possess anti-knockproperties superior to those of motor fuels produced by non-catalytic orthermal cracking, catalytic cracking soon came into prominence. Thedevelopment of aviation soon created a demand for motor fuels having notonly anti-knock characteristics superior to those of motor fuelsproduced by thermal cracking, but possessing also morev desirableoverall properties and, particularly, a greater stability with referenceto gum formation during use and storage.

It is well known to those familiar with the art, that catalytic crackingof petroleum stocks has been carried out mostly in the vapor phase and 3Claims. (Cl. 196-52) having desired boiling ranges. As a consequence,the supplyof available catalytic cracking stocks is restricted.

As is well known in the art, even recycle stocks obtained from thecatalytic cracking of non-refractory petroleum cracking stocks, are notsuited to recycling to the catalytic cracking zone to be subjected tothe catalyic cracking operation per se or in conjunction with the chargestocks, due to their somewhat refractory nature. Accordingly, theserecycle stocks frequency have been processed separately, in thermalcracking operations, as distinguished from cracking operations whereincracking catalysts are employed. As noted hereinbefore, gasolineproduced by catalyticcracking operations is somewhat superior togasoline produced by thermal cracking operations. Hence, and in view ofthe foregoing, only a moderate portion of the total yield ofhydrocarbons boiling'within the gasoline boiling range, may be ob- Thepresent invention is to be distinguished from those processes for theproduction of arcmatic hydrocarbons from the cracking of petroleum oils,wherein in order to minimize the production of benzene in preference toalkyl aromatic hydrocarbons, the concentration of henzene is increasedabove that produced by the normal formation of benzene in the crackingzone. The present invention is not directed to a process for theproduction of aromatic hydrocarbons or of cyclic hydrocarbons, butrather, it is directed to an improved catalytic cracking operation forthe production of high yields of hydrocarbons boiling within thegasoline boiling range. It must be noted that the gasoline produced inaccordance with the present invention, is the somewhat superiorproductor that resulting from catalytic cracking operations.

Accordingly, it is an object of the present invention to provide amethod for converting heavy liquid hydrocarbons into light, normallyliquid hydrocarbons. Another object is to provide an improved method ofcatalytic cracking. A further object is to afiord an eflicient methodfor efiecting the catalytic cracking of petroleum stocks of a refractorynature. A very important object is to provide a method ofcatalyticcracking, where.- .7

object is to provide a method of catalytic cracking capable of carryingout the foregoing objects by subjecting petroleum cracking stocks'tocat-' alytic cracking in the presence ,ofthermally-stable aromatichydrocarbons. Othenobjects and advantages of the present invention willbecome ap-' liquid hydrocarbons -.under cracking conditions,

with'acracking catalyst, inthepresence of an added aromatic hydrocarbon.that is thermally stable under said cracking. conditions.

According to ourinventiomany aromatic hydrocarbon which is 'stableat thetemperatures mdinarily used in thermal and catalytic crackingoperations, is suitable for our purpose. Benzene,meihylbenzene,naphthalene, and diphenyl may be mentioned byway ofnon-limiting'examplesol the aromatic hydrocarbons employed.

In the preferred embodiment of our invention, we use'benzene asthe-thermally stablearomatic hydrocarbon. Accordingly, benzene may becharged together with the petroleum cracking stock, intothecracking-zone. I In the cracking zone, thestock is subjected to-thecracking conditions and converted in the desired manner. The benzenevapors emerge from the cracking zone unchanged alongwiththe: products ofthe cracking operation, and together, they are sent through a fractionalcondensation system to condense the desired fractions oflower-boilinghydrocarbons thatihave been-produced, an'd also, a benzenefraction. .The benzene'fraction ordinarilyconstitutes a substantiallycomplete recovery of benzene, and'thisfraction may be convenientlyrecycled to the cracking zonewith freshpetroleum cracking stock.

Generally speaking, the-conversion of heavy, normally liquidhydrocarbons into light, normally liquid hydrocarbons by pyrolysis, withor Without the use of cracking catalysts, at temperatures of the orderof about 800 F. to aboutl100 F., and

at pressures determined by the phase of operadue'to the fact that therate of cracking of these -latter stocks is rmuch higher than that ofthe 4 with the method of our invention, are any of the well knownpetroleum cracking stocks for thermal cracking or catalytic crackingoperations, although the advantages of the method of the presentinvention, are more predominant when the heavier and more refractorypetroleum cracking stocks are employed. For instance, benzene can beused to advantage in the cracking of heavy residua for the sole purposeof gasoline production. For example, the cracking of heavy petroleumresidua, of the order of A. P, I. gravity 10 and lower, is performedwith considerable difficulty because of excessive coke formation. Theuse of fractions from these heavy residua as the recycling stock forsuch cracking operations, does not .give .satisfactory results,.-sincethese fractions f,thems'elves;'have undesirable coke-forming properties.On the other hand, the use of other rrecycle stocks having higher A. P.I. gravity, for

such ,crackingoperations, is practically impossible '-'.,heavy-residua.Benzene, however, is highly re- :fractory and accordingly. does not formcoke under-thecracking-conditions; as a matter of fact, benzene,actuallytends to diminish coke forma- .f-tion. .As stated hereinbefore,benzene can be recovered and recycled and, particularly because of itstendency to reduce coke formation, it constitutes an attractive additivein catalytic cracking processes wherepthec amount of coke depositregulates the. requirements for catalyst regeneration.

.A feature .of themethodof the present invention, is that ,the yields:per pass :of hydrocarbons boiling within the gasoline-boiling range,other variables-such as temperature, contact time of the petroleumstock; inzthe catalyst bed, etc., remaining constant; are unusuallyhigh.Theprior art did notrsuccessiully crack heavy stocks under thetemperature conditions of the present invention.Suchhigh:temperaturetconditions in the absence of. added-benzeneleaditovery excessive coke and gas formation .with lresultant low yields ofgasoi line.

Accordingly,=i=another feature of our method, is that severexcraeking.conditions may be employed. It is well known thatithe'octane number ofmotor fuels increases rapidly with increasing severity of-cracking.Howeven severe cracking conditions are normally avoided in conventionalcommercial operations due to practical considerations arising fromexcessive 'cokean'd gas formation. The use 0fi'bEI1Zne, aS -S8t forthhereinbefore, minimizes coke and gas formation; hence, our invention thepresent invention,it is our belief that benzene enters into the crackingreaction during the early stages ofthe operation, by functioning as ahydrogen and: alkyLradical 'facceptor," and is subsequently regeneratedby dehydrogenation I and dea'lkylation.

A most important feature of this invention, is totalchargeibenzene-l-stock) or or 0.167 based that b our method, catalyticcracking of refracon the cracking stock. Under similar conditions, torystocks is rendered commercially feasible. but In the absence f n such acrackin Even extremely efr ctor stocks of the type stock would be soseverely cracked that the yield duced in thermal cracking and reformingopera- 5 3g 5 3, 3; 33:32 gfii gz gggfifgig' tions gwes qiutesatlsfactqy i of 9 I very high. The use of very severe conditions of ascompared to those obtainable in processes of catalytic cracking suchv asF. and a space the prmr velocity of 0.167, in the presence of benzene,is To illustrate the methodof our invention and to 1 an advantage'ofthemethod of our invention.

. Table II Stock: Recycle stock from runs 1 through? Catalyst: Activatedclay I Iiecycle I volume Tem- Rate Gas Coke Gasoline Stock 210 ResiduumRun 0 H pcra- L [L Wt. Wt. to 200 c. 300 0. 300 0. Sw N o. a ture, g Percent Per cent Vol. Per Fraction I Vol. Per 6 H I F. Stock Stock c'entStock V01. Per cent Stock P 19 3 0? 1 .f

1 Benzene was carefully fractionated out of gasoline cut in range 70-950. and analyzed for purity. Impurities are included in gasoline yieldand amount to about 10% of total gasoline cut. v

point out the advantages thereof, we set forth in These data illustratethe efiect of. benzene on Table I, II, III, IV and V, data obtained incarthe cracking of refractory stocks, n: this inrying out our method ofcatalytic cracking. stance, the recycle stock-from the-cracking of aTable I Stock: Naphthenic distillate for cracking" from Coastal crude A.P. I.=3u.2 I I 8p. gr. (so/00 F.=0.875 v r 1 I A. S. '1. M.distillation: f I I I. B. P.==440 F. 1 r Y l0%=468 F 50%=504 F 90%=555 FE. P.=584 F. Catalyst: Activated clay Recycle v I 'lcm- Rat Gas CokeGasoline Stock 200- Residuum Run 3 Derajfi' Wt. Wt. to 200 0. 300 0. 0000. f No. 2 ture, I Per cent Percent Vol. Per Fraction VoL'Per 6 3 L F.Stock Stock cent Stock Vol. Per cent Stock cent Stock m Brge $411 92510/20 15. 0 4. 3- 51. 1 35.4 3. 9 '91. 5' 34:1 025 v/20 1.0 2. 0 Y 48.840.9 2.0 90.1 1:1 950 I 20/20 11. 6 2. 6 49. 6 42. 7 3. 4 96. 6 1:1 92510/20 12.6 6.0 52.8 34.4 2.5 95.8 1:1 900 10/20 12. 0 5. S 54. 2 36. 72. 9 90. 2 2:1 Q 10/20 11. 4 5. 1 58. 7 30. 1 5. 2 95. 5 2:1 925 20/208.4 2.4 53.6 50.3 6.0 93.8

1 Benzene was carefully fractionated out of gasoline cut in range C. andanalyzed for purity. Impurities are included in gasoline yield andamountto about 10%0i' total gasoline cut. I I II I The data in Table I-show that the yieldsiof typical cracking stock. The. yield per'pass ofgasoline per pass, considering the temperatures .gasoline from thisrecyclestock is 88.2% as and contact times of the petroleum stock-intheagainst 52.8% obtained ith thevirginstbck.

. I I Table In Stock: Dewaxed distillate I: I

A. P. I.=27.7

Sp. gr. (SO/60 F'.==0.889 I Oatalyst: Activated clay I Recycle I I Tem-I Gas Coke Gasoline Stock 200- Residuum ;?259' Run 0 H pera- .Wt. Wt. to200 0. -300O. 300C. P i N c. 2 ture, i Per cent Per cent Vol. PerFraction Vol. Per C F. I Stock Stock cent Stock Vol. Per cent Stock ingcent Stock i Benzene Was careinllyfractlonated out of gasoline cut inrange 7095 C.and analyzed for purity. Impurities are included in gasolne yield and amount to about 10% of total gasoline cut. I I v 1catalystbed, are abnormally high; For example, These data show that theyields of gasoline iii- F run NO. '7 shows a gasoline yield-0f,58.7% perpass crease with. decreasing'severity. of cracking cone at 925 F. and-aspace velocity;nice-based on 'Tdltluns, such'asshorter contact titties."

""S." U." V. at 210 Ed 53.1 eatalystz nctivatedclay 5 f- Recycle H Re.volume {Pai 1B8. I Gas poke gasoline Stocked) fnesidunm a Run C'Ho-pera-- LJL Wt Wt to-200 G. 300 C. 300 Per cent :No.; ture'g. Percent..Per,'ecent "VoLEPer Fraction VoLPer PFQ, fg k. .Stock centStock; vneer .centstock gflgfi f cent Stock 11 1:1 92 12/20 17. 6 ll-I6 52. 8l4. 4 l3. 6 99. 2 l2 1:1 950 20/20 16.6 10.2 46.4 15.6 20.4 p 97.6 13.02:1 925 20/20 10.0 8.0 58;!- 7 1652 21. 4 "97.8

I Benzene was carelully'irectionated out oi? gasoline cut in range 704)?C. and analyzed for purity. Impurities areincluded gwoline yieldand-amount to about of total gasoline cut.

These data show :that the'yiel'ds of gasoline attic-hammer coonditionsof catalytic cracking inincrease with decreasing severity of crackingcluding .a temperature varying between about conditions, in instance,lower temperatures. 800 F. and about 1100 F., with a catalyst pro- TableV emerg e1 gstgbkfrom D'e'Flore'z vapor pbaso cracking of'Miran'docrude.

A. S. T. M. distillation: 1. B 0 F.

Recycle C H Ref volume Tem- Rate Gas Coke Gasoline Stook:20u-= LResrduumRun Cm p ra- LIL we. Wt. to 200 0. 300" 0. 300 0. No. stock ture,Oat/hr. Per cent Per cent Vol. Per Fraction Vol. Per

F Stock Stock cent Stock Vol. Per cent Stock cent Stock in Charge lBenzene was carefully fractionated out of gasoline cut in range 7095 C.and analyzed for purity. Impurities are included in gasoline yield andamount to 'about l0% of total gasoline cut.

These data illustrate one cot-the most striking motingcrackingundersaidconditions of catafeatures of the method of our-invention, namely "lyticcracking.

that even extremely refractcrycharge.stocksgive 2. .A method.forcobtaining high yields-of hysatisfactory yields of gasoline. 7 45drocarbons boiling within theug'asoline boiling The figures given on therecovery of pure *range from a recycle .petroleum' crackingstock benzenecan be considered to be {quite reliable j=having an A. P. I. gravity ofless than about 15, if the basic assumption that benzene doesnotwhich'comprises 'contacting amixtureconsisting contribute to gas andcoke formation, is correct. essentially of said recycle petroleumcracking This assumption was verified by runs with benstock and addedbenzene, inamountsofat least zene alone and is valid at temperaturesbelow abouteohe-half volume of addedtbenzene :to one about 950 F. and inthe range of space rates volume of'--said"recyclepetroleumcracking'stock" indicated, under conditions .of catalyticicra'ckingjncluding This application is .a continuationsin-pa'rt ofatemperature varying between about 800.F.andour copending.ap'p'licationi'Serial .Number 366,806, 5 about 51100. E, with acatalystpromotingcracke filedNovember23;'I940, now abandoned. ingunder saidconditions of catalytic cracking.

Although the present invention has been 'de- 3. A method for obtaininghigh yields of hydroscribed in conjunction with preferredeiiibodicarbons boiling within the gasoline boiling range ments, it isto be understood that modifications from a recycleipetroleumcrackingstock having and variations may be resorted to without de- 6 an A. P.-I.; .gravity oflless than about 15, which parting from the spirit andscope of the invencomprises"contacting -amixture consisting essentionasthose-skilledintheart'willreadiiy under- 'tially"ofsaidrecyclepetroleum cracking stock stand. t Such variations and modifications areand an added aromatic hydrocarbon selected consideredtoibe withinthepurview-andv scope of from thegroup consisting of benzene, alkyl benthe.appended claims. zenepnaphthalene, and 'diphenyl, in amounts of Weclaim: at least about one-half volume of added aro-.1...A.method.for.obtaining highyields of hydro- A matichydrocarbonto-cne-volume of said recycle carbons boiling within-the gasolineboiling range petroleum cracking stock, under conditions of from arecycle petroleum cracking stock having catalyticcracking including atemperature varyan A. -P.-I.gravity-of less-than about 15", which ingbetween about 800 F. and about 1100 F.,

comprises contactingamixtureconsisting essenwith :a, .catalyst promotingcracking under said tially of said recycle petroleum cracking stockconditions of catalytic cracking.

and added :benzene iin :amounts varying between RGWLAND C. *I-IANSFORD.about /2 atosabout 2'-.volumes% ofradded benzene to I ll. SACHANEN.

one volume 1.0! .wsaidirecycle.petroleum rcracking :75 :ms gu foubwinpagg) REFERENCES CITED Number The following references are of record inthe file of this patent:

UNITED STATES PATENTS 6 Number Number Name Date 795,125

2.245.157 Pier et al. I June 10. 1941 Name Date Pier et a]. II Aug. 1'7,1943 Marschner 1 Nov. 30, 1943 FGREIGN PATENTS Country Date France Mar.4, 1936

